(1) Field of Invention
This invention relates to nonaqueous liquid fabric treating compositions. Particularly, this invention relates to nonaqueous liquid laundry detergent compositions which have good detergency and softening properties and which are stable against phase separation and gelation and are easily pourable and to the use of these compositions for cleaning and softening soilded fabrics.
More particularly this invention relates to a liquid detergent-softening composition and a method for cleaning and softening fabrics in the wash cycle of a laundering operation. Specifically, the present invention relates to detergent-softening compositions adapted for use in the wash cycle of a laundering operation, the composition including an acid terminated nonionic surfactant and a water dispersible cationic quaternary ammonium compound softening agent, and a nonionic surfactant.
(2) Discussion of Prior Art
Compositions useful for treating fabrics to improve the softness and feel characteristics thereof are known in the art.
When used in domestic laundering, the fabric softeners are typically added to the rinse water during the rinse cycle having a duration of only from about 2 to 5 minutes. Consequently, the consumer is required to monitor the laundering operation or take other precautions so that the fabric softener is added at the proper time. This requires the consumer to return to the washing machine either just prior to or at the beginning of the rinse cycle of the washing operation which is obviously burdensome to the consumer. In addition, special precaution has to be taken to use a proper amount of the fabric softener so as to avoid over dosage which may render the clothes water repellant by depositing a greasy film on the fabric surface, as well as imparting a certain degree of yellowness to the fabrics.
As a solution to the above-noted problems, it has been known to use fabric softeners which are compatible with common laundry detergents so that the softeners can be combined with the detergents in a single package for use during the wash cycle of the laundering operation. Examples of such wash cycle added fabric softening compositions are shown in U.S. Pat. Nos. 3,351,438, 3,660,286 and 3,703,480 and many others. In general, these wash cycle fabric softening compositions contain a cationic quaternary ammonium fabric softener and additional ingredients which render the softening compounds compatible with the common laundry detergents.
There have been many disclosures in the art relating to detergent compositions containing cationic softening agents, including the quaternary ammonium compound softening agents, and nonionic surface-active compounds. As representative of this art, mention can be made of U.S. Pat. Nos. 4,264,457, 4,239,659, 4,259,217, 4,222,905, 3,951,879, 3,360,470, 3,351,483, 3,644,203, etc. In addition, U.S. Pat. Nos 3,537,993, 3,583,912, 3,983,079, 4,203,872 and 4,264,479 specifically disclose combinations of nonionic surface-active agent, cationic fabric softener and another ionic surfactant or modifier, such as zwitterionic surfactants, amphoteric surfactants, and the like.
While many of these prior art formulations provide satisfactory cleaning and/or softening under many different conditions they still suffer from the defects of not providing adequate softening--e.g. comparable to rinse cycle --added softeners.
U.S. Pat. No. 3,920,565 discloses a liquid rinse cycle fabric softener composition containing 2 to 15% of a cationic fabric softener and 0.5 to 4.0% of an alkali metal salt of a fatty acid of from 16 to 22 carbon atoms (soap) and optionally, up to 2% of a nonionic emulsifier, the balance water. The dihigher alkyl dimethyl ammonium chlorides are the preferred cationics, although mono-higher alkyl quats are also mentioned.
It is generally accepted in the art that the mono-higher alkyl quaternary ammonium compounds, such as, for example, stearyltrimethyl ammonium chloride, being relatively water soluble, are less effective softeners than the dihigher alkyl cationic quaternary softeners (see, for example, U.S. Pat. No. 4,326,965), and, therefore, their use in conjunction with, for example, anionic detergents, such as fatty acid soaps, with which they are capable of forming softening complexes has been suggested for use as rinse cycle fabric softeners.
It is also known from U.S. Pat. No. 3,997,453 that stable, fabric softening compositions having improved dispersibility in cold water as used in the rinse cycle, are provided by a cationic quaternary ammonium compound, as the sole softener, and an anionic sulfonate at a weight ratio of cationic to anionic of from about 80:1 to 3:1. This patent discloses both mono-higher and dihigher alkyl cationic quaternary softening compounds and also discloses alkyl benzene sulfonates as the anionic compound. According to the '453 patent, the addition of minor amounts of the anionic sulfonate to water dispersions of the excess amount of quaternary softener reduces the viscosity of the dispersion and produces a homogeneous liquid which is readily dispersible in cold water (i.e. the rinse cycle of an atomatic washing machine).
As mentioned above, however, it has been recognized for some time that it would be highly desirable as a matter of convenience to employ the fabric softening formulation concurrently with the detergent in the wash cycle of the washing machine.
U.S. Pat. No. 4,222,905 to Cockrell, Jr. discloses laundry detergent compositions which may be in liquid form and which are formulated from certain nonionic surfactants and certain cationic surfactants, including mono-higher alkyl quaternary ammonium compounds, such as tallowalkyltrimethyl ammonium halide, at a nonionic:cationic weight ratio of from 5:1 to about 1:1. This patent teaches that the amount of anion-producing materials should be minimized and preferably totally avoided.
Nonionic/cationic mixed surfactant detergent compositions having a nonionic:cationic weight ratio of from about 1:1 to 40:1 in which the nonionic surfactant is limited to the class having a hydrophilic-lipophilic balance (HLB) of from about 5 to about 17, and the cationic surfactant is limited to the class of mono-higher alkyl quaternary ammonium compounds in which the higher alkyl has from about 20 to about 30 carbon atoms, are disclosed by Murphy in U.S. Pat. No. 4,239,659. This patent provides a general disclosure that other adjunct components may be included in their conventional art-established levels for use which is stated to be from about 0 to about 40%. A broad list of adjunct components is given including semi-polar nonionic, anionic, zwitterionic and ampholytic cosurfactants, builders, dyes, fillers, enzymes, bleaches, and many others. There are no examples using, and no disclosure of, anionic surfactants; however, it is stated that the cosurfactants must be compatible with the nonionic and cationic and can be any of the anionics disclosed in U.S. Pat. No. 4,259,217 to Murphy.
Liquid nonaqueous nonionic heavy duty laundry detergent compositions are also well known in the art. For instance, compositions of that type may comprise a liquid nonionic surfactant in which are dispersed particles of a builder, as shown for instance in the U.S. Pat. Nos. 4,316,812, 3,630,929 and 4,264,466 and British Pat. Nos. 1,205,711, 1,270,040 and 1,600,981.
The related pending applications assigned to the common assignee are Ser. No. 687,815 filed Dec. 31, 1984; Ser. No. 597,793 filed Apr. 6, 1984; Ser. No. 597,948 filed Apr. 9, 1984; Ser. No. 767,568 filed Aug. 02, 1985; Ser. No. 687,816 filed Dec. 31, 1984; and Ser. No. 661,775 filed Oct. 17, 1984.
The applications are directed to liquid nonaqueous nonionic laundry detergent compositions.
Liquid detergents are often considered to be more convenient to employ than dry powdered or particulate products and, therefore, have found substantial favor with consumers. They are readily measurable, speedily dissolved in the wash water, capable of being easily applied in concentrated solutions or dispersions to soiled areas on garments to be laundered and are non-dusting, and they usually occupy less storage space. Additionally, the liquid detergents may have incorporated in their formulations materials which could not stand drying operations without deterioration, which materials are often desirably employed in the manufacture of particulate detergent products. Although they are possessed of many advantages over unitary or particulate solid products, liquid detergents often have certain inherent disadvantages too, which have to be overcome to produce acceptable commercial detergent products. Thus, some such products separate out on storage and others separate out on cooling and are not readily redispersed. In some cases the product viscosity changes and it becomes either too thick to pour or so thin as to appear watery. Some clear products become cloudy and others gel on standing.
The present inventors have been involved in studying the behavior of nonionic liquid surfactant systems with particulate matter suspended therein. Of particular interest has been nonaqueous built laundry liquid detergent compositions and the problem of settling of the suspended builder and other laundry additives as well as the problem of gelling associated with nonionic surfactants. These considerations have an impact on, for example, product stability, pourability and dispersibility.
It is known that one of the major problems with built liquid laundry detergents is their physical stability. This problem stems from the fact that the density of the solid particles dispersed in the nonionic liquid surfactant is higher than the density of the liquid surfactant.
Therefore, the dispersed particles tend to settle out. Two basic solutions exist to solve the settling out problem: increase nonionic liquid viscosity and reduce the dispersed solid particle size.
It is known that suspensions can be stabilized against settling by adding inorganic or organic thickening agents or dispersants, such as, for example, very high surface area inorganic materials, e.g. finely divided silica, clays, etc., organic thickeners, such as the cellulose ethers, acrylic and acrylamide polymers, polyelectrolytes, etc. However, such increases in suspension viscosity are naturally limited by the requirement that the liquid suspension be readily pourable and flowable, even at low temperature. Furthermore, these additives do not contribute to the cleaning performance of the formulation.
Grinding to reduce the particle size provides the following advantages:
1. Specific surface area of the dispersed particles is increased, and, therefore, particle wetting by the nonaqueous vehicle (liquid nonionic) is proportionately improved.
2. The average distance between dispersed particles is reduced with a proportionate increase in particle-to-particle interaction. Each of these effects contributes to increase the rest-gel strength and the suspension yield stress while at the same time, grinding significantly reduces plastic viscosity.
The yield stress is defined as the minimum stress necessary to induce a plastic deformation (flow) of the suspension. Thus, visualizing the suspension as a loose network of dispersed particles, if the applied stress is lower than the yield stress, the suspension behaves like an elastic gel and no plastic flow will occur. Once the yield stress is overcome, the network breaks at some points and the sample begins to flow, but with a very high apparent viscosity. If the shear stress is much higher than the yield stress, the pigments are partially shear-deflocculated and the apparent viscosity decreases. Finally, if the shear stress is much higher than the yield stress value, the dispersed particles are completely shear-deflocculated and the apparent viscosity is very low, as if no particle interaction were present.
Therefore, the higher the yield stress of the suspension, the higher the apparent viscosity at low shear rate and the better is the physical stability against settling of the product.
In addition to the problem of settling or phase separation, the nonaqueous liquid laundry detergents based on liquid nonionic surfactants suffer from the drawback that the nonionics tend to gel when added to cold water. This is a particularly important problem in the ordinary use of European household automatic washing machines where the user places the laundry detergent composition in a dispensing unit (e.g. a dispensing drawer) of the machine. During the operation of the machine the detergent in the dispenser is subjected to a stream of cold water to transfer it to the main body of wash solution. Especially during the winter months when the detergent composition and water fed to the dispenser are particularly cold, the detergent viscosity increases markedly and a gel forms. As a result some of the composition is not flushed completely off the dispenser during operation of the machine, and a deposit of the composition builds up with repeated wash cycles, eventually requiring the user to flush the dispenser with hot water.
The gelling phonomenon can also be a problem whenever it is desired to carry out washing using cold water as may be recommended for certain synthetic and delicate fabrics or fabrics which can shrink in warm or hot water.
The tendency of concentrated detergent compositions to gel during storage is aggrevated by storing the compositions in unheated storage areas, or by shipping the compositions during winter months in unheated transportation vehicles.
Partial solutions to the gelling problem have been proposed, for example, by diluting the liquid nonionic with certain viscosity controlling solvents and gel-inhibiting agents, such as lower alkanols, e.g. ethyl alcohol (see U.S. Pat. No. 3,953,380), alkali metal formates and adipates (see U.S. Pat. No. 4,368,147), hexylene glycol, polyethylene glycol, etc. and nonionic structure modification and optimization. As an example of nonionic surfactant modification one particularly successful result has been achieved by acidifying the hydroxyl moiety end group of the nonionic molecule. The advantages of introducing a carboxylic acid at the end of the nonionic include gel inhibition upon dilution; decreasing the nonionic pour point; and formation of an anionic surfactant when neutralized in the washing liquor. Nonionic structure optimization has centered on the chain length of the hydrophobic-lipophilic moiety and the number and make-up of alkylene oxide (e.g. ethylene oxide) units of the hydrophilic moiety. For example, it has been found that a C.sub.13 fatty alcohol ethoxylated with 8 moles of ethylene oxide presents only a limited tendency to gel formation.
Nevertheless, improvements are desired in both the stability and gel inhibition of nonaqueous liquid fabric treating compositions.